Page:Proceedings of the Royal Society of London Vol 2.djvu/55

Rh even by Scheele, for apples contain a portion of sorbic as well as of malic acid; but that these acids are different, Mr. Donovan proves by decomposing malate of lead by sorbic acid. For if water be boiled on malate of lead, no crystals are to be obtained on cooling the liquor; but when the malate is boiled in sorbic acid, the malate is decomposed; and the liquor, when cooled, deposits the peculiarly brilliant crystals of sorbate of lead.

In order to be well assured of the difference between these acids, Mr. Donovan compared his acid with as many as seven different specimens of malic acid obtained from different sources, and was confirmed in the opinion that they are essentially different, by comparison of various neutral salts obtained from each; those containing sorbic acid being in general to be procured in permanent crystals, while those from malic acid yield merely deliquescent residua when reduced to dryness.

The author remarks, that the purest malic acid is that prepared from the Sempervivum tectorum, which, according to the observation of Vauquelin, appears to be free from every other acid; while the juice of apples, unless they be taken very young, appears constantly to contain a portion of sorbic acid.

This paper concludes with conjectures respecting the progressive changes of vegetable products, and possible conversion of bitter principle into malic acid, sorbic acid, and oxalic acid; but the author is fully sensible that little reliance can be placed on such speculations. 



The genera of animals here enumerated by the author, are the Lamprey, Myxine, an animal between the Lamprey and the Myxine, the Aphrodita aculeata, and the Leech.

In the Lamprey, the organs of respiration consist of separate oval bags, that have seven openings on each side of the neck, for receiving and emitting the water which they breathe by means of a cartilaginous thorax surrounding the bags. In the Lampern, which is of the same genus, the structure is very similar, but the cartilages of its thorax are weaker.

In an animal brought from the South Sea by Sir Joseph Banks, there are also the same number of external openings, and the same number of bags; but there is no cartilaginous thorax, and hence the author is induced to consider the animal intermediate between the Lamprey and Myxine, which it resembles in having teeth, and in having a mesentery to its intestines.

In the Myxine, there are only two orifices on the under surface of the neck; but these branch internally to six separate bags on each side.